Laterally diffused metal oxide semiconductor (LDMOS) devices are used in power application devices because the devices are easily integrated in BIPOLAR-CMOS-DMOS (BCD) processes and can extend the voltage capability of the technology with the laterally diffused junction device. For example, high voltage LDMOS devices may be used in lighting, motor control and switch-mode power supply applications. LDMOS devices rely on a shallow conduction layer formed under a LOCOS (“local oxidation of silicon”) region or a STI (shallow trench isolation) region to handle the higher drain voltage, when the device is biased.
The on-state resistance (“RON”) and the maximum breakdown voltage (“BVDSS”) of the device are two (2) important characteristics of LDMOS designs. These characteristics are important for the operating parameters for the LDMOS devices, which dictate the applications in which the devices may be used. On-state resistance is typically dependent upon the design/layout of the device, the process condition, temperature, diffusion length, and the various materials used to fabricate the devices. Breakdown voltage is defined as the largest reverse voltage that can be applied to a diode (e.g., a p-n junction) without causing an exponential increase in the current of the diode.